In 2007, D.C. residents were diagnosed with HIV at a rate of nearly four per day. That rate dropped to less than one resident per day in 2016.

The 74 percent decline in new cases — from 1,333 in 2007 to 347 in 2016 — can be attributed to factors that include a needle-exchange program, condom distribution and increasing use of preventive medication to halt the spread of the disease, city officials said Tuesday.

“I’m pleased to say we have made considerable progress, but I don’t have to tell you there is more work to do,” Mayor Muriel E. Bowser (D) said at a news conference at the Whitman-Walker Health community clinic on 14th Street NW.

The District remains in an HIV/AIDS epidemic, officials said. About 13,000 people in Washington, or 1.9 percent of the population, are living with HIV, according to an annual report from the D.C. Health Department. The World Health Organization defines a generalized epidemic as a disease affecting at least 1 percent of the population.

But efforts undertaken by the city — including distributing more than 6 million male and female condoms in 2016 and removing more than 800,000 needles from the street — are helping to make progress, Health Department Director LaQuandra Nesbitt said.

The needle-exchange program, which helped reduce the number of drug-related HIV diagnoses from 149 in 2007 to seven in 2016, is one example of the city’s success, Nesbitt said.

“Just seven cases — it’s stunning,” Bowser said.

Possible changes by Congress to the Affordable Care Act are not expected to alter the status of the city’s needle-exchange program, she said. From 1998 to 2007, Congress blocked the District from allocating local tax dollars for ­needle-exchange efforts.

The group most affected by the virus in the District are black men who have sex with men, Nesbitt said. Women are the second most-affected group, she said. Last year, the District began the nation’s first campaign to encourage black women to begin taking the prophylactic drug known as PrEP, which drastically cuts the risk of contracting HIV. PrEP is shorthand for pre-exposure prophylaxis.

Bowser on Tuesday announced the launch of a new campaign — “UequalsU,” which stands for “undetectable equals untransmittable” — to promote treatment of HIV as a way to prevent the spread of the virus.

Sustained treatment that reduces a patient’s viral load level, a measure of the concentration of the virus that is in a patient’s blood, makes it unlikely that the patient will pass the virus to someone else, according to a study in the New England Journal of Medicine.

The campaign seeks to remind residents to take their medication regularly so they do not transmit HIV to others. Ads featuring pictures of couples and using the tag­line, “YOU are the solution,” will appear on buses across the city, Bowser said.

Bowser released a plan in December aimed at combating the city’s HIV/AIDS epidemic. The effort, dubbed the 90/90/90/50 plan, calls for having 90 percent of HIV-positive District residents aware of their status, 90 percent of those who have been diagnosed receiving treatment and 90 percent who are in treatment reaching viral-load suppression by 2020.

The ultimate goal is to reduce the number of new diagnoses to 185 or fewer by 2020, which would be a 50 percent drop from the number of new cases in 2015.